Conventionally, a motorcycle is provided with an intake pipe which extends rearwardly from the engine, and an air cleaner or like devices disposed beneath the rider's seat. This arrangement inevitably increases the length of the pipe of intake system, resulting in an increased first and last length of engine. In order to obviate this shortcoming of the prior art, it has been proposed to extend the intake pipe upwardly directly from the engine. In such a case, the air cleaner must be disposed under or between the draping sides of the fuel tank, which in turn reduces the capacity or volume of the fuel tank. Particularly in the case of a motorcycle having a V-type engine, the piping arrangement of intake and exhaust systems are inconveniently complicated. This gives rise to the demand for air intake conduitry with a simple and compact arrangement of its pipes.